1. Field of the Invention
The invention relates to an apparatus for safely transporting spent nuclear fuel and other hazardous materials and, more particularly, to a rail transportation system for safely transporting spent nuclear fuel and other hazardous waste materials to interim storage facilities, transfer points, or to a final federal disposal site, the rail transportation system including a railcar and cask cradle.
2. Description of the Related Art
Nuclear reactors and storage sites for radioactive materials have been in operation for many years. In a nuclear reactor, the fissionable material gradually becomes spent and must be removed along with other radioactive byproducts. Since the spent fuel contains fission by products which are highly radioactive and which generate large amounts of heat, the spent fuel is usually temporarily stored in the reactor's spent fuel pool. The spent fuel pool is a pool of water of sufficient volume to prevent the escape of harmful radiation and to absorb and dissipate the heat generated by the decaying fissionable material. Alternatively, the spent fuel may be temporarily stored in a hot cell. A hot cell refers to a heavily shielded structure having the capability to prevent the escape of harmful radiation, while absorbing and dissipating the heat generated by the spent fuel.
Generally, there is limited storage space in a nuclear reactor's spent fuel pool or in its hot cell. Thus, the spent fuel must be moved to a storage site to make room for additional spent fuel. In some cases, there is a desire to shut the nuclear reactor down and remove all fissionable material, in which case, all of the fissionable material must be removed to a storage site. Conventionally, spent nuclear fuel has been stored at various locations across the country. Spent nuclear fuel has been transported by storing it in small groups using multiple fuel storage drums. The spent fuel may be transported in the form of spent fuel rods or in the form of rubble. Conventionally, spent fuel rod assemblies have been transported in fuel transportation containers designed for undamaged fuel rod assemblies. The foregoing attempted solution, however, has required that substantially fewer failed fuel rod assemblies be transported per container, compared to the number of undamaged fuel rod assemblies that can be transported in the same container. By transporting fewer failed fuel rod assemblies, even if some fissionable material escapes from the failed fuel rods and accumulates near other fissionable material in the container, there is not enough fissionable material in the entire container to pose a significant risk of criticality. The problem with the foregoing solution, though, is it wasteful of resources, because significantly fewer failed fuel rod assemblies can be transported per container relative to the number of undamaged fuel rod assemblies that can be transported in the same container.
Another, attempted solution has been to transport failed fuel rod assemblies in fuel transportation containers designed for transporting fissionable material in the form of rubble. That is, the fissionable material is not in the form of rods, but is in the form of small particles. Thus, the failed fuel rods are broken up into rubble, and placed in the container. The problem with this solution, however, is that the method is inefficient for three principle reasons. First, the failed fuel rod assemblies be broken up. Second, such containers are capable only of transporting comparatively few failed fuel rod assemblies. Finally, the transportation container is only designed for transportation, not storage. Thus, once the fissionable material has been transported to another location, the container must be unloaded in a fuel pool or in a hot cell, and other arrangements made to store the fissionable material.
The other major problem with transporting spent nuclear fuel is that United States law imposes stringent safety requirements even on containers used to transport undamaged fuel rod assemblies. The relevant law imposes significantly more restrictive requirements with respect to the transportation of spent nuclear fuel across areas accessible to the public, as opposed to areas inaccessible to the public.
State of the art spent fuel transportation containers for areas accessible to the public are casks with individual compartments. The fuel rod assemblies are loaded into individual compartments in the casks in a spent fuel pool or a hot cell. The purpose of the individual compartments within each cask is to ensure sufficient spacing between adjacent fuel rod assemblies to avoid any danger of criticality. The fuel rod assemblies are loaded into the cask in a spent fuel pool or hot cell. Upon reaching the storage location, the fuel rod assemblies must be removed from the cask in a spent fuel pool or hot cell, and then stored.
In contrast, state of the art spent fuel transportation containers for areas inaccessible to the public are typically a sealed canister placed within a cask. The fuel rod assemblies are loaded into individual compartments in a canister in a spent fuel pool or a hot cell. The canister is then sealed and placed in a cask. When the cask/canister assembly reaches the storage site, the canister is removed from the cask, stored, and the cask may be reused, which is a much more efficient process.
Nonetheless, the cask/canister method cannot be used for transportation in areas accessible to the public because they fail to meet the requirements imposed by U.S. law. Whether the spent fuel is transported by cask or a sealed canister within a cask, there is a significant need for the casks to be transported in a safe and efficient manner so as to eliminated the possibility of hazardous materials leaking into the environment. Accordingly, there is a need for an invention that provides for the transportation and storage of spent fuel rod assemblies, and for a cask/canister device for the transportation and storage of spent fuel across areas accessible to the public. The present invention provides a solution, wherein a existing casks can be used and can be safely transported resulting in much greater efficiency in the transportation over public thoroughfares and storage of spent nuclear fuel.